Overlooked contribution to the Hall effect in ferromagnetic metals

It is pointed out that in ferromagnetic metals a contribution to the Hall voltage arises when a nonzero spin current exists, which is generally the case in the presence of a charge current. This contribution is independent of any scattering effects and exists down to zero temperature. The sign of the resulting Hall coefficient may be either equal or opposite to the one of the ordinary Hall coefficient depending on the band filling. This effect seems to have been left out in previous analyses of the Hall effect in ferromagnetic metals.